Comprehensive mapping of the exterior architecture of the dromedary camel brain

The morphological perspective of the camel brain remains largely unexplored. Therefore, studying the topography of the camel brain is of crucial importance. This study aimed to provide a detailed color-coded topographic representation of the camel brain's gross anatomy and nomenclature, showing its various gyri and sulci and their borders. We compared them to previously known information to develop a detailed description of camel brain exterior architecture. Our research identified distinctive gyri and sulci with discrete positions and surrounding structures, allowing us to define sulci boundaries and establish logical gyri nomenclature. This study uncovered previously overlooked gyri and sulci and improved descriptions of specific sulci. The ectomarginal sulcus, splenial sulcus, splenial gyrus, and ectogenual gyrus are a few examples. These findings highlight several unique anatomical features of the dromedary brain, which can guide future research. By providing a comprehensive examination of the distinctive exterior anatomical features of the camel brain, this study may serve as a point of convergence for all researchers, providing more accurate identification of the gyri and sulci.


Sulci of the dromedary brain
The cortical surface of the camel's brain hemisphere is complexly folded, and the main sulci exhibit a wide range of ramifications that may complicate their identification.
In our detailed examination of the cerebral hemispheres of the Dromedary camel, we observed a complex and distinct network of sulci.The intricate cerebral sulci that mark the brain's exterior and demarcate its gyri present a distinct pattern of cerebral folding.

Sylvian fissure
Our observations revealed that the sylvian fissure in the dromedary brain is the most prominent and deepest sulcus on the lateral surface of its hemisphere.It is short, almost vertical, arises ventrally near the piriform lobe, and runs dorsally, giving three main branches.The rostral limb extends rostrodorsally to the original sylvian fissure.The middle limb extends dorsally up to the level of the middle ectosylvian sulcus.Lastly, the caudal limb seems longer and runs caudodorsally (Fig. 2).The sylvian fissure and limbs delineate the sylvian gyrus's border and its respective sections.The rostral limb delineates the rostral sylvian gyrus, the middle one intersects the middle sylvian gyrus, and the caudal limb marks the border between the middle and the caudal sylvian gyrus (Fig. 2).

Presylvian sulcus
Our findings show that the presylvian sulcus extends rostroventrally on the lateral hemisphere.This sulcus originates within the frontal lobe and is connected to the sylvian fissure caudally.It is situated dorsolaterally to the rhinal sulcus and delineates the dorsal border of the prorean gyrus as it runs rostrally until it meets the cruciate sulcus (Fig. 2).

Rhinal sulcus
The rhinal sulcus is the most ventrolateral sulcus in the camel's cerebral hemispheres.The rhinal sulcus and the olfactory fissure outline the olfactory region of the forebrain.The rhinal sulcus has two segments.The first segment runs as a direct extension of the olfactory fissure, curving slightly dorsally before merging with the presylvian sulcus before encountering the sylvian fissure.The second segment called the caudal rhinal sulcus, begins around the pyriform lobe and extends caudally.This segment was left unmentioned in previous camel brain research, highlighting the novel insights provided by our findings (Fig. 2).

Ectosylvian sulcus
The ectosylvian sulcus has a deep and curved path within the lateral hemisphere.It is located ventral to the suprasylvian sulcus.It tends to make a caudal and rostral arch around the sylvian fissure (Fig. 2).Our observations revealed that this sulcus has three limbs, each with distinct orientations.The rostral limb begins from the middle ectosylvian sulcus and runs slightly parallel and caudally to the rostral limb of the suprasylvian sulcus.The middle limb is ventrally positioned relative to the suprasylvian sulcus' middle limb.Interestingly, the caudal limb has a longer tract and is unconnected to the middle limb.It runs perpendicularly in a curvy manner ventral to the caudal branch of the suprasylvian sulcus.We observed the sulcus is situated between the caudal sylvian gyrus and the caudal ectosylvian gyrus (Fig. 2).

Suprasylvian sulcus
It is a large and deep sulcus that roughly separates the cerebral surface into dorsal and lateral sections.It is located dorsal to the ectosylvian and Sylvian sulci.It extends rostrocaudally in an undulating pattern.We observed that the suprasylvian sulcus of the Dromedary camel's brain subdivides into three distinct segments.These have been appropriately named the rostral, middle, and caudal portions, each with distinct characteristics (Fig. 2).The rostral limb of the suprasylvian sulcus begins laterally and runs dorsally until it merges with the middle limb.The latter runs rostrocaudally at the middle of the cerebral hemisphere, and the caudal limb runs until it reaches the occipital lobe.The caudal limb of the suprasylvian sulcus runs parallel to the marginal sulcus (Fig. 2).

Diagonal sulcus
The diagonal sulcus is situated dorsolaterally to the presylvian sulcus.It begins close to the coronal sulcus and runs caudoventrally toward the sylvian fissure.The diagonal sulcus defines the dorsal border of the diagonal gyrus (Fig. 2).

Ectomarginal sulcus
In all examined cerebral hemispheres, the ectomarginal sulcus displays a dual-component portion.The caudal part of the sulcus is situated ventrolateral to the marginal sulcus; the other portion is positioned almost dorsolateral to the suprasylvian sulcus.Following a caudal extension, the sulcus is interrupted before resuming a shorter path, aligning almost parallel to the caudal limb of the suprasylvian sulcus (Figs. 1 and 2).

Marginal sulcus
Our investigation identified the marginal sulcus as the most prominent and distinct sulcus visible on the dorsal surface.It has a considerable depth and runs parallel to the longitudinal fissure.It begins at the middle of the hemisphere and runs further caudally in a wavy fashion until the occipital pole (Figs. 1 and 2).

Endomarginal sulcus
Our investigation identified the endomarginal sulcus as a thin sulcus positioned in the hemisphere's most caudodorsal region.It shows a brief stretch parallel to the longitudinal fissure, forming the most medial structure relative to the longitudinal fissure within the cerebrum's caudal region.It is flanked laterally by the caudal portion of the marginal sulcus (Figs. 1, 3, and 4).

Ansate sulcus
The ansate sulcus is a deep groove with a relatively short span.It is located dorsally, nearly at the hemisphere's midpoint.It extends laterally from the longitudinal fissure.Along its tract, it meets the coronal sulcus rostrally and the ectomarginal sulcus on its lateral end (Figs. 3 and 4).

Coronal sulcus
The coronal sulcus emerges dorsally, around the frontal lobe.It projects in a rostral and lateral route, thereby defining the lateral boundary of both the post-cruciate and pre-cruciate gyri.In its caudal direction, the coronal sulcus intersects with the ansate sulcus (Figs. 1, 2, and 4).

Cruciate sulcus
Our investigation revealed that the cruciate sulcus is located dorsally in the most rostral part of the hemisphere.This sulcus, characterized by its relatively short course, extends transversely towards the longitudinal fissure.It emerges rostrally around the midpoint of the coronal sulcus.It is located between the post-cruciate gyrus, which is found caudally to the sulcus, and the pre-cruciate gyrus, positioned rostrally (Figs. 3 and 4).
In the medial view of the dromedary camel cerebrum, we observed numerous sulci displaying diverse features.These sulci vary in characteristics, ranging from delicate and superficial to complex structures with multiple branches.The prominent structure in this view is the corpus callosum, which connects the right and left cerebral hemispheres (Fig. 3).In our study, we meticulously examined and described the various sulci in the medial aspect, as reported below.

Callosomarginal sulcus
We identified the callosomarginal sulcus as one of the most prominent structures recognizable in the medial view of the dromedary brain.The callosomarginal sulcus is characterized by its considerable length and appearance as a medial extension of the cruciate sulcus, extending caudally with a wavy pattern.The middle segment of this sulcus is situated dorsally and almost parallel to the callosal sulcus.Caudally, the callosomarginal sulcus eventually meets with the entomarginal sulcus (Fig. 3).

Entomarginal sulcus
The entomarginal sulcus, situated dorsocaudally, and the endomarginal sulcus make up the endomarginal and entomarginal gyri.Initially, this sulcus follows a short and straight route before taking a sharp ninety-degree turn in a ventral direction towards the tectum.The endomarginal sulcus is a shorter structure in a dorsal position relative to the entomarginal sulcus (Fig. 3).

Callosal sulcus
Our study revealed that this sulcus delineates the corpus callosum, differentiating it from the adjacent cingulate gyrus.The callosal sulcus contributes to forming the deeper portion of the longitudinal fissure (Fig. 3).

Genual sulcus
As observed in our study, the genual sulcus runs in a rostral direction parallel to the callosal sulcus.It is situated between the genual and the cingulate gyrus.Just before the ascending segment of the genual sulcus, we identified the ectogenual sulcus, which borders the ectogenual gyrus (Fig. 3).

Cerebral gyri
In our study, we precisely identified, described, and characterized the cerebral gyri in the dromedary camel's brain, presenting our findings through detailed figures capturing multiple view aspects, providing a comprehensive visualization of these gyri within the cerebral structure (Figs. 1, 4, 5 and 6).

Sylvian gyrus
Our study found the sylvian gyrus located dorsal to the olfactory tract and piriform lobe.It has three parts, namely the rostral, middle, and caudal parts, surrounded by the ectosylvian sulcus.The rostral part is separated from the middle part by the rostral ramus of the sylvian fissure.The middle sylvian gyrus is separated from the caudal part by the caudal ramus of the sylvian fissure.The middle ramus of the sylvian fissure is located right above the lateral fissure and divides the middle sylvian gyrus into two parts.The rostral and caudal parts entirely encompass the insular region of the cerebrum (Fig. 5).

Ectosylvian gyrus
Our findings show that the ectosylvian gyrus is located below the suprasylvian gyrus and has three parts: the rostral, middle, and caudal.The rostral part meets the coronal gyrus from its rostral end.The middle part is surrounded by the rostral suprasylvian gyrus from the rostral margin and the caudal suprasylvian gyrus from its caudal end.The caudal part of the ectosylvian gyrus meets the occipital gyrus and the caudal sylvian gyrus from its caudal and rostral margins, respectively (Fig. 5).

Suprasylvian gyrus
The suprasylvian gyrus is subdivided into two distinct rostral and caudal sections.These parts are completely seen from the lateral view and separated by the middle part of the ectosylvian gyrus.The rostral part is located

Occipital gyrus
The occipital gyrus, located in the caudal portion of the occipital lobe, is situated beneath and caudal to both the caudal part of the suprasylvian gyrus and ectomarginal gyrus (Figs. 5 and 6).

Ectomarginal gyrus
Our observations reveal that the ectomarginal gyrus is situated laterally to the marginal gyrus, composed of rostral and caudal parts.These two sections are seen to converge laterally with the caudal portion of the suprasylvian gyrus (Figs. 1 and 5).

Marginal gyrus
The marginal gyrus is located laterally to the longitudinal fissure of the cerebrum.It extends from the end of the post-cruciate gyrus or the ansate sulcus to the caudal end of the cerebrum (Figs. 1, 4, 5, and 6).Starting from the caudal third of each cerebral hemisphere, a thin endomarginal gyrus (Figs. 1, 4, and 6) intervenes between the marginal gyrus and the longitudinal fissure and extends until the transverse fissure.Both gyri are more prominent in the dorsal view, even though some parts can be observed on the medial aspect of the hemispheres.
From its lateral end, the marginal gyrus separately encompasses the rostral and caudal parts of the ectomarginal gyrus (Figs. 1 and 5).

Post-cruciate gyrus
This gyrus is found caudal to the cruciate sulcus and is separated from the marginal sulcus by the ansate sulcus.
It is dorsocaudal to the pre-cruciate gyrus.Unlike the pre-cruciate gyrus, a significant part of this gyrus can be seen on the medial side, above the genual gyrus (Figs. 1, 4, 5, and 6).

Pre-cruciate gyrus
Our findings show that this gyrus is caudal to the prorean gyrus and rostral to the cruciate sulcus.The rostral view reveals most of this gyrus, with more minor remnants visible in both the medial and lateral views (Figs. 1, 4, 5, and 6).

Coronal gyrus
In the anterodorsal region of the brain, the coronal gyrus can be found between the longitudinal fissure and the coronal sulcus.It is located lateral to the post-cruciate sulcus, and from a lateral perspective, it extends up to the edge of the diagonal gyrus.From its rostral border, the coronal gyrus meets the post and pre-cruciate gyri.This gyrus is partially seen from the medial view (Figs. 1, 4, 5, and 6).

Prorean gyrus
It is the most rostral gyrus positioned at the base of the frontal lobe.It is bordered dorsally by the presylvian sulcus.It can be fully seen from the rostral view.A part of the prorean gyrus is located on the lateral side, dorsal to the olfactory nerves (Figs. 4 and 5).

Diagonal gyrus
This gyrus is dorsal to the prorean gyrus, between the diagonal and presylvian sulci.The diagonal gyrus marks the caudal transition from the olfactory area to the large piriform lobe of the rhinencephalon (Figs. 4 and 5).

Cingulate gyrus
Positioned within the medial aspect of the dromedary hemisphere, the cingulate gyrus is found immediately surrounding the corpus callosum, the part of the brain where the left and right cerebral hemispheres meet and communicate.The callosal sulcus separates the cingulate gyrus from the corpus callosum.The rostral half of the cingulate gyrus is separated from the genual gyrus by the genual sulcus, while the caudal half is separated from the other gyri found dorsally by the callosomarginal sulcus (Fig. 6).

Subcallosal gyrus
Our findings revealed that the subcallosal gyrus is located at the rostral extremity of the cingulate gyrus, directly beneath the genu of the corpus callosum.The rostral part of the subcallosal gyrus is defined from the ventral part of the genual gyrus by the genual sulcus (Fig. 6).

Genual gyrus
The genual gyrus surrounds the cingulate and subcallosal gyri rostrally.It exhibits a wide dorsal part that gradually tapers towards the ventral portion of the gyrus.The ventral part of this gyrus is wider than the middle part.
The post-cruciate gyrus can be found here surrounding the genual gyrus dorsally.The most rostral part of the genual gyrus meets the pre-curciate gyrus, which is better seen from the lateral view.The middle-tapered part of the genual gyrus adjoins the ectogenual gyrus (Fig. 6).

Entomarginal gyrus
The entomarginal gyrus is a compact gyrus found above the splenial gyrus and below the marginal gyrus rostrally and the endomarginal gyrus caudally (Fig. 6).It is a gyrus presented horizontally along the dorsocaudal portion of the medial cerebral hemisphere.

Splenial gyrus
The splenial gyrus is a medially situated structure located between the entomarginal gyrus dorsally and the caudal portion of the cingulate gyrus ventrally (Fig. 6).It is found around the caudodorsal portion of the medial surface of the brain.

Discussion
Comprehensive morphological studies of the dromedary brain, particularly its gyri and sulci, are notably lacking compared to the extensive information available for other animal species.In this study, we mapped the sulci and gyri of the camel brain based on previous neuro-anatomical studies 9,10,12,13 , incorporating contemporary anatomical nomenclature 11 .The gyral boundaries were determined by analyzing the arrangement and interrelationships of adjacent sulci.Additionally, we further refined our gyral identifications using cerebral arterial branches 3,14,15 .While a few earlier studies have tentatively explored the external architecture of the camel brain, inconsistencies can be observed between their findings 9,10 .For example, Xie and Wang 10 identified the orbital gyrus, while Kanan 9 labeled the same structure as the prorean gyrus.Additionally, Xie and Wang 10 mentioned the gyrus post-cruciatus, which Kanan 9 referred to as the posterior sigmoid gyrus.Likewise, the dorsal cingulate gyrus, as described by Xie and Wang 10 , corresponds to the fornicalus gyrus, as labeled by Kanan 9 .Both studies did not comprehensively describe all sulci and gyri of the camel brain; each presented partial accounts of sulci and gyri of the camel brain.Kanan 9 sometimes employed human terminology, such as naming the sylvian fissure as the central sulcus, a term used in human anatomy.Consequently, our study provided a comprehensive colored-coded atlas of the brain morphology of the onehumped camel (Camelus dromedarius), specifically focusing on describing and identifying its gyri and sulci.Our study established a solid foundation for further research in this area, bridging the gaps left by previous literature.
Our analysis revealed subtle variations in brain anatomy among the samples studied, particularly in the size and folding patterns of gyri and the depth of sulci in individual specimens.These findings align with the observations made by Tecirlioğlu 17 , Thompson 18 , Taner 19 , and Kurt 20 , suggesting that the sulci and gyri on the left and right hemispheres of the same animal species can differ in terms of their shapes and numbers.
The camel brain shares features with other mammals, displaying typical ungulate characteristics, such as the neocortex's intense gyrification 10 .These authors also highlight that while the camel brain's weight is relatively lighter than that of horses and water buffaloes, it is still heavier than that of certain cattle species 10 .The camel brain's exterior structure resembles an equine species more than any other species 9 .However, the camel's brain has less folding than that of horses, characterized by intense gyrification and cortical thickness 21 .
While the brain of the camel shares several similarities with that of the equines 9 , it also reveals a combination of convolutional patterns from two different suborders of Ungulata, namely, Artiodaclyla and Perissodactyla 9,22  www.nature.com/scientificreports/Although the camel neopallium was highly heterogeneous in its surface architecture, certain sulci were characteristic in their length, depth, and course, indicating that they were structurally distinct, constant, and almost invariable.These landmarks serve as a reliable guide for topographic orientation.With the help of our thorough study, we could clearly and topographically describe the distinct chain of sulci that runs throughout the whole stretch of the camel neopallium from all perspectives (lateral, medial, and dorsal views).
Our findings indicate that the sylvian fissure of the dromedary brain, commonly referred to as the lateral sulcus 9 , is a prominent groove that defines the boundaries between the temporal, frontal, and parietal lobes.The sylvian fissure displays distinct characteristics as it ascends from the temporal lobe dorsally, including a shorter length, relatively narrow width, and a more linear trajectory.This pattern of the sylvian fissure is also observed in horses 23 .In contrast, the sylvian fissures in ox are considerably deeper and nearly reach the middle of the lateral hemisphere 22 .
Based on our findings, the sylvian fissure gives three limbs: the rostral, middle, and caudal ramus.The middle ramus of the sylvian fissure follows a relatively straight pathway, extending from the sylvian fissure toward the top of the brain.This exhibits a parallel pattern in other ruminants, such as bovines and ovines 22,24 .This sulcus in horses displays a more curved shape resembling the Greek letter "omega" and is particularly deep and prominent 23 .We have observed that the central sulcus described by Kanan 9 is, in fact, the middle ramus of the sylvian fissure.Hence, the term 'middle ramus of the sylvian fissure' better describes the location and pathway of this sulcus, aligning it with the nomenclature used in humans.
Our study revealed that the rhinal sulcus in camels' cerebral hemispheres is positioned as the most ventrolateral sulcus.We found that the rhinal sulcus is divided into two segments.The first segment originates directly from the olfactory fissure and has a slight dorsal curve before merging with the presylvian sulcus and the sylvian fissure.The second segment, the caudal rhinal sulcus, starts at the pyriform lobe and extends caudally (Fig. 2).It is worth noting that previous studies on camel brain anatomy did not extensively explore this particular area, highlighting its overlooked significance.
We observed that the suprasylvian sulcus was distributed extensively over the laterodorsal surface of the cerebral hemisphere.Camels have a notably shallow and simpler suprasylvian sulcus, whereas horses have a deeper suprasylvian sulcus with several branches 21 .
Our investigation found that the dorso-caudal portion of the hemisphere's surface is distinguished by a collection of three sulci, namely the marginal, ectomarginal, and endomarginal sulcus, which are positioned side by side.Among them, the marginal sulcus is positioned centrally, flanked by the ectomarginal sulcus on its lateral side and the endomarginal sulcus on its medial side (Fig. 1).However, in certain specimens, we observed that the caudal segment of the marginal sulcus varied in length and course, making it unpredictable.It either followed a slightly longer lateral course towards the caudal side of the hemisphere, or it occasionally encountered an interruption near its dorsocaudal pole, failing to extend continuously toward the caudomedial surface.This observation contradicts the terminology used by Kanan 9 , where what we now identify as the ectomarginal sulcus was referred to as the parietooccipital fissure.This sulcus should be named "ectomarginal sulcus" due to its location and after comparing it to those of other animal species, providing a more accurate representation of this sulcus in the dromedary brain 11 .
In our study, the detailed names of the gyri were given according to the position and continuity of the sulci that separate them.The sylvian gyri are divided into anterior, dorsal, and posterior parts, similar to the nomenclature used in humans 9 , while we used the terms rostral, middle, and caudal based on the N.A.V 11 to name the sulci and gyri found on the lateral surface of the dromedary brain.
The ectosylvian and suprasylvian gyrus in horses had more complex structures with more prominent gyri and sulci, and subregions compared to the same region in the camel brain 25,26 .The occipital gyrus in horses is particularly well-developed and has many branches and subregions, while in camels, it appears less complex 21,23 .
According to Kanan 9 , the prorean gyrus is well-marked and is located on the dorsorostral border of the frontal lobe.However, in our research, it was found that it is located lateroventrally above the olfactory nerve.
Our analysis revealed notable discrepancies in the nomenclature used for sulci and gyri observed in the medial view of the camel's brain as described in the existing literature.Specifically, we found that Kanan 9 referred to the genual gyrus as the gyrus fornicatus, suggesting that previous studies may have applied human nomenclature when labeling certain sulci and gyri in the camel's cerebral hemisphere 9,10 .The callosomarginal sulcus was identified by Xie and Wang 10 in their study as being placed dorsal to the actual callosomarginal sulcus, which encircles the cingulate gyrus as observed in our study (Fig. 6).To ensure consistency with the terminology used to name this sulcus in other animals, as reported in other studies, we have revealed that the name splenial sulcus is more precise.According to our findings, a component that Xie and Wang 10 referred to as the entogenual sulcus is better defined as being a part of the callosomarginal sulcus.We also suggest reclassifying the gyrus that was previously known as the orbital gyrus.We have named it the ectogenual gyrus because of its proximity to the ectogenual sulcus (Fig. 6).
Our study also challenged the terminology used to indicate the dorsal and ventral cingulate gyri as the two separate portions of the cingulate gyrus 10,27 .Based on our observations, we use the term cingulate gyrus to refer to what Xie and Wang 10 refer to as the ventral cingulate gyrus.We have discovered that the area referred to by Xie and Wang 10 as the dorsal cingulate gyrus is the entomarginal gyrus (Fig. 6).The latter terms are consistent with the descriptions given by Kanan 9 and Blanco 27 in addition to other research on many animal species [22][23][24]28 , which we believe provides a clearer anatomical representation of these gyri.
In conclusion, our research offers a comprehensive investigation into the gyri and sulci of the dromedary brain, a relatively understudied area in the literature.Our research identified previously overlooked components and enhanced the descriptions of specific structures like the ectomarginal sulcus, splenial sulcus, splenial gyrus, and ectogenual gyrus.These findings demonstrate the importance of further exploration in comparative neuroanatomy, emphasizing the need to develop a comprehensive reference dataset for camel brain anatomy.

Figure 1 .
Figure 1.Dorsal view of the Dromedary camel brain.This figure provides a detailed representation of the gyri on the left cerebral hemisphere while highlighting the sulci on the right hemisphere.

Figure 2 .
Figure 2. Detailed illustration of the various colored sulci on the lateral aspect of the dromedary camel's brain.

Figure 3 .
Figure 3. Medial view of the right dromedary cerebral hemisphere, illustrating the intricate arrangement of sulci on the medial surface.

Figure 4 .
Figure 4. Different gyri and sulci of the cerebral hemispheres as seen from the rostrodorsal view.

Figure 5 .
Figure 5. Detailed illustration of the gyri on the lateral surface of the Dromedary camel brain.

Figure 6 .
Figure 6.Medial view of the right dromedary cerebral hemisphere, illustrating the intricate arrangement of gyri on the medial surface.